Background: Dendritic cell (DC)-based vaccine is a promising approach for cancer therapy. Pioneer trials have been conducted using DC generated in research conditions. There is now a need for generating DC in clinical grade conditions, including the use of closed systems, avoidance of FCS and respect of good manufacturing practices (GMP).
Methods: DC were generated from 84 leukapheresis products of 27 cancer patients enrolled in two Phase I/II trials of vaccination of either MAGE+tumors (n = 24) or prostate cancer (n = 3). Monocytes were seeded in culture bags in a serum-free medium supplemented with IL-4 and GM-CSF. After a 7 day culture, DC were collected and most were pulsed with various MAGE-derived peptides.
Results: After a short leukapheresis (mean time: 66 min; mean processed blood: 5 L), a mean of 6 x 10(9) WBC were collected, from which 2.25 x 10(9) were seeded. The culture procedure yielded a large number of DC (mean: 62 x 10(6) DC) harboring the expected phenotype of immature DC (CD1a(+) CD14(-) HLA-DR(+) CD80(+) CD86(+) CD83(-)). This phenotype was not altered by peptide loading. These DC, either fresh or thawed, were functionally effective invitro. Their s.c. and i.v. injections were devoid of any short-term side effect and associated with the induction of immune responses in the patients.
Discussion: Large numbers of functional immature clinical grade DC can be generated in a closed system from leukapheresis products in cancer patients. These results provide the basis for large-scale studies of cancer immunotherapy under improved safety conditions.